CVD flowable gap fill

ABSTRACT

The present invention meets these needs by providing improved methods of filling gaps. In certain embodiments, the methods involve placing a substrate into a reaction chamber and introducing a vapor phase silicon-containing compound and oxidant into the chamber. Reactor conditions are controlled so that the silicon-containing compound and the oxidant are made to react and condense onto the substrate. The chemical reaction causes the formation of a flowable film, in some instances containing Si—OH, Si—H and Si—O bonds. The flowable film fills gaps on the substrates. The flowable film is then converted into a silicon oxide film, for example by plasma or thermal annealing. The methods of this invention may be used to fill high aspect ratio gaps, including gaps having aspect ratios ranging from 3:1 to 10:1.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/508,461, filed Jul. 23, 2009, titled “CVD FLOWABLE GAP FILL,” issuedas U.S. Pat. No. 7,915,139, which is a continuation of U.S. patentapplication Ser. No. 11/323,812, filed Dec. 29, 2005 also titled “CVDFLOWABLE GAP FILL,” issued as U.S. Pat. No. 7,582,555, all of which areincorporated herein by reference in their entireties.

BACKGROUND OF THE INVENTION

This invention relates to electronic device fabrication processes. Morespecifically, the invention relates to chemical vapor depositionprocesses for forming dielectric layers in high aspect ratio, narrowwidth recessed features.

It is often necessary in semiconductor processing to fill a high aspectratio gaps with insulating material. This is the case for shallow trenchisolation, inter-metal dielectric layers, passivation layers, etc. Asdevice geometries shrink and thermal budgets are reduced, void-freefilling of high aspect ratio spaces (e.g., AR>3:1) becomes increasinglydifficult due to limitations of existing deposition processes.

Most deposition methods deposit more material on the upper region thanon the lower region of a sidewall and/or form top-hats at the entry ofthe gap. As a result the top part of a high aspect ratio structuresometimes closes prematurely leaving voids within the gap's lowerportions. This problem is exacerbated in small features. Furthermore, asaspect ratios increase, the shape of the gap itself can contribute tothe problem. High aspect ratio gaps often exhibit reentrant features,which make gap filling even more difficult. One such problematicreentrant feature is a narrowing at the top of the gap. The etchedsidewalls slope inward near the top of the gap. For a given aspect ratiofeature, this increases the ratio of gap volume to gap access area seenby the precursor species during deposition. Voids and seams formation ismore likely under these conditions. If the top of the gap prematurelycloses off, a chemical etch is required to re-open the gap before morefilm can be deposited in the gap.

One approach to gap fill is high-density plasma chemical vapordeposition (HDP CVD). HDP CVD is a directional (bottom-up) CVD processthat is used for high aspect ratio gap-fill. The method deposits morematerial at the bottom of a high aspect ratio structure than on itssidewalls. It accomplishes this by directing charged dielectricprecursor species downward, to the bottom of the gap. Nevertheless, someoverhang or top-hat formation still results at the entry region of thegap to be filled. This results from the non-directional depositionreactions of neutral species in the plasma reactor and fromsputtering/redeposition processes. The directional aspect of thedeposition process produces some high momentum charged species thatsputter away bottom fill. The sputtered material tends to redeposit onthe sidewalls. Limitations due to overhang formation become ever moresevere as the width of the gap to be filled decreases and the aspectratio increases.

HDP CVD processes rely on plasma etch steps to remove sidewall depositsand top-hats. Typically a fluorine species, such as NF₃, is used betweendielectric film deposition steps to etch the film. After a layer ofdielectric partially fills gaps on a substrate, the fluorine-containingplasma etches the layer to remove top-hats and open the gap for furtherdeposition. However, these etch steps may be inappropriate in someapplications.

Alternative dielectric deposition processes that can fill high aspectratio features of narrow width, reduce sidewall and top-hat formationand eliminate the need for etch steps during dielectric deposition wouldbe desirable.

SUMMARY OF THE INVENTION

The present invention meets these needs by providing new methods offilling gaps. In certain embodiments, the methods involve placing asubstrate into a reaction chamber and introducing a vapor phasesilicon-containing compound and oxidant into the chamber. Reactorconditions are controlled so that the silicon-containing compound andthe oxidant are made to react and condense onto the substrate. Thechemical reaction causes the formation of a flowable film, in someinstances containing Si—OH, Si—H and Si—O bonds. The flowable film fillsgaps on the substrates. The flowable film is then converted into a finalsilicon oxide film, for example by plasma or thermal annealing. Themethods of this invention may be used to fill high aspect ratio gaps,including gaps having aspect ratios ranging from 3:1 to 10:1.

One aspect of the invention relates to a method of depositing adielectric film on a substrate, the method involving the steps of a)placing the substrate in a reaction chamber; b) introducing a processgas comprising a silicon-containing compound and an oxidant; and c)exposing the substrate to the process gas under conditions such that thesilicon-containing compound and the oxidant react to form a flowablefilm on the substrate surface. In certain embodiments, the methodfurther involves converting the flowable film into a solid dielectricmaterial (e.g., a silicon oxide film). In certain embodiments,conversion of the film may be accomplished by annealing the as-depositedfilm by a thermal or plasma anneal.

Another aspect of the invention relates to a method of filling gaps on asubstrate with dielectric material. The method involves the steps of a)placing the substrate in a reaction chamber; b) introducing a processgas comprising a silicon-containing compound and an oxidant; c) exposingthe substrate to the process gas under conditions such that thesilicon-containing compound and the oxidant react to form a flowablefilm in the gap; and d) converting the flowable film to a dielectricmaterial.

Another aspect of the invention relates to a method of filling gaps on asubstrate with dielectric material that involves the operations of a)placing the substrate in a reaction chamber; b) introducing a processgas comprising a silicon-containing compound into the reaction chamber;c) exposing the substrate to the process gas under conditions such thata silicon-containing film is deposited in the gaps via a plasma-assistedreaction; d) introducing an oxidant into the reaction chamber; e)exposing the silicon-containing film to the oxidant such that a flowablefilm comprising Si—H, Si—O and Si—OH bonds is formed in the gaps; and e)converting the as-deposited film to a dielectric material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a rough schematic cross-sectional diagram of a trenchpartially filled by a conventional method.

FIG. 2 is a process flow diagram depicting a method according to oneembodiment of the invention.

FIG. 3 is a process flow diagram depicting a method according to oneembodiment of the invention.

FIGS. 4 and 5 are block diagram depicting some components of variousreactors suitable for performing certain embodiments of the invention.

FIG. 6 shows an embodiment of the reaction chamber utilizing a baffleplate assembly to increase precursor utilization.

FIG. 7 shows FTIR spectra of a dark-deposited film before and afterexposure to an oxygen plasma.

FIG. 8 is a microscope image showing circular growth of the flowablefilm caused by a completed reaction between the silicon and oxidantprecursors.

FIG. 9 is a microscope image showing irregular growth of the flowablefilm caused by incomplete reaction between silicon and oxidantprecursors due to the presence of an alcohol inhibitor.

DETAILED DESCRIPTION OF THE INVENTION Introduction

The present invention relates to deposition processes that providecomplete gap of fill high aspect ratio (typically at least 3:1), narrowwidth gaps.

Most deposition methods either deposit more material on the upper regionthan on the lower region of a sidewall or form cusps (also calledtop-hats) at the entry of the gap. To remove sidewall and top-hatdeposits and keep the gap open for further deposition, conventional HDPCVD processes typically use a multi-cycle deposition process-etchprocess. Each cycle includes a deposition step followed by an etch stepTypically, fluorine species are used in the etch step. These fluorineetch steps are costly and time-consuming, in some cases requiringmultiple reactors.

FIG. 1 shows a rough schematic of a trench partially filled by aconventional HDP CVD method. Reference number 101 indicates wheresidewalls have formed from film that has been sputtered away from thebottom of the trench and redeposited on the sidewalls of the trench.These sidewalls have pinched off preventing further deposition. Achemical etch is required to re-open the trench before dielectric filmcan be deposited in it. Multiple deposition-etch-deposition cycles arenecessary to fill high aspect ratio trenches or other features.Reference number 103 indicates a weak spot. Conventional gap fillmethods often lead to the formation of weak spots in the dielectricfilm. Weak spots may form as a result of the increased gap volume to gapaccess area as the gap closes off, and can lead to voids or seams in thegap and ultimately device failure.

Other known methods of gap-fill also rely on multi-cycle depositionmethods and are susceptible to pinch-off at the top of the gap, and voidand seam formation in the gap.

The present invention provides single-cycle gap-fill methods that resultin good, seamless and void-free gap fill. The methods involve depositinga soft jelly-like liquid or flowable film and then converting theflowable film into a solid silicon oxide film. The methods of thepresent invention eliminate the need for etch steps.

Process

FIG. 2 is a process flow sheet depicting a method according to oneembodiment of the present invention. As shown, a deposition process 200begins at operation 201 in which a substrate containing a gap isprovided to a reaction chamber. Providing the substrate to the reactormay involve clamping the substrate to a pedestal or other support in thechamber. For this purpose, an electrostatic or mechanical chuck may beemployed.

After the substrate is provided to the reaction chamber, a process gasis introduced at operation 203. The process gas includes asilicon-containing compound and an oxidant. The gas may also include oneor more dopant precursors. Sometimes, though not necessarily, an inertcarrier gas is present. In certain embodiments, the gases are introducedusing a liquid injection system. Typically the silicon-containingcompound and the oxidant are introduced via separate inlets. In certainembodiments the oxidant is doped with a compound that contributes toreducing the reaction rate at the wafer surface. Examples of dopantcompounds that reduce the reaction rate include alcohols, e.g., ethanoland isopropyl alcohol. Reducing the reaction rate at the wafer surfacemay be desirable to facilitate continuous film propagation and growth.Also, in certain embodiments, the reactants may be provided in mannerthat increases residence time over the wafer surface. For example, insome embodiments, an inert gas (e.g., He, Ar or N₂) ballast is providedto increase reactant utilization. The ballast is provided below a baffleplate assembly. This constricts the flow of reactants thereby increasingtheir resident time over the wafer substrate.

The substrate is then exposed to the process gas at operation 205.Conditions in the reactor are such that the silicon-containing compoundand the oxidant react and condense. As shown in operation 207, aflowable film is thereby deposited on the substrate surface. Thesubstrate is exposed to the process gas for a period sufficient todeposit a flowable film to fill the gap. The deposition processtypically forms soft jelly-like film with good flow characteristics,providing consistent fill. The deposited film may also be describedherein for the purposes of discussion as a gel having liquid flowcharacteristics, a liquid film or a flowable film.

Process conditions in the reactor are such that the reaction productcondenses on the surface. In many embodiments, this involves bringingthe substrate into the chamber under “dark”, i.e., non-plasmaconditions. The substrate is not exposed to a plasma during thedeposition phase (steps 205 and 207) of the process. Although notindicated on the flow sheet, gaseous byproducts may be continuouslypumped from the reaction chamber.

After the flowable film has been deposited in the gap, the as-depositedflowable film is converted to a silicon oxide dielectric film inoperation 209. In some embodiments, the film is converted by exposure toa plasma containing, for example, one or more of oxygen, helium, argonand water.

Process Parameters

Process Gas

The process gas contains a silicon-containing compound and an oxidant.Suitable silicon-containing compounds include organo-silanes andorgano-siloxanes. In certain embodiments, the silicon-containingcompound is a commonly available liquid phase silicon source. In someembodiments, a silicon-containing compound having one or more mono, di,or tri-ethoxy, methoxy or butoxy functional groups is used. Examplesinclude, but are not limited to, TOMCAT, OMCAT, TEOS, tri-ethoxy silane(TES), TMS, MTEOS, TMOS, MTMOS, DMDMOS Diethoxy silane (DES),triphenylethoxysilane, 1-(triethoxysilyl)-2-(diethoxymethylsilyl)ethane,tri-t-butoxylsilanol and tetramethoxy silane. Examples of suitableoxidants include ozone, hydrogen peroxide and water.

In some embodiments, the silicon-containing compound and the oxidant aredelivered to the reaction chamber via liquid injection system thatvaporizes the liquid for introduction to the chamber. The reactants aretypically delivered separately to the chamber. Typical flow rates of theliquid introduced into a liquid injection system range from 0.1-5.0mL/min per reactant. Of course, one of skill in the art will understandthat optimal flow rates depend on the particular reactants, desireddeposition rate, reaction rate and other process conditions.

Acceptable silicon-containing compound/oxidant flow ratios are veryvariable, as there is typically only a single reaction. Examples ofsuitable ratios include 3:1-1:100.

The flowable film deposited on the substrate typically contains somecombination of Si—O, Si—H and Si—OH bonds. As discussed above, in manyembodiments, the reaction of the silicon-containing compound and theoxidant takes place in non-plasma conditions. The absence of RF power(or other plasma source) prevents the incorporation of organic groups inthe film. For example, in reaction between TES and steam, the chemicalreaction causes formation of a flowable film containing Si—OH, Si—H andSi—O bonds, while the ethoxy group is removed as a gaseous ethanolbyproduct. As discussed above with respect to FIG. 1, the byproduct iscontinuously pumped out.

As indicated above, in certain embodiments a chemical reagent that actsas an inhibitor to slow down the reaction between the silicon andoxidant precursors is used. Examples of such reagents include alcoholssuch as ethanol, isopropyl alcohol, etc. Ethanol is a by-product of theoriginal chemical reaction as shown in the equation below between thesilicon-containing precursor H—Si—(O—C₂H₅)₃ and the oxidant H₂O:

While not being bound by any particular theory, it is believed that theproviding ethanol along with the oxidant precursor causes the reactionto be slowed down due to only two of the ethoxy groups on thesilicon-containing precursor being converted. It is believed that theremaining ethoxy groups serves to network the film by acting as a link.Depicted below is one embodiment of this method using a 25-90% molarsolution of ethanol:

Film composition depends in part on the oxidant chosen, with a weakeroxidant (e.g., water) resulting in more Si—H bonds than a strongeroxidant (e.g., ozone). Using ozone will result in conversion of most ofthe Si—H bonds to Si—OH bonds. An exemplary reaction according to oneembodiment of the invention between an organo-silane precursor(R_(4-x)—SiH_(x)) and peroxide (H₂O₂) produces a silanol gel(R—Si(OH)_(x) as well as other byproducts that may be pumped out.

Deposition Reaction Conditions

Reactions conditions are such that the silicon-containing compound andoxidant, undergo a condensation reaction, condensing on the substratesurface to form a flowable film.

As discussed above, the reaction typically takes place in dark ornon-plasma conditions. Chamber pressure may be between about 1-100 Torr,in certain embodiments, it is between 5 and 20 Torr, or 10 and 20 Torr.In a particular embodiment, chamber pressure is about 10 Torr.

Substrate temperature is typically between about −20 and 100 C. Incertain embodiments, temperature is between about 0 and 35 C. Pressureand temperature may be varied to adjust deposition time; high pressureand low temperature are generally favorable for quick deposition. Hightemperature and low pressure will result in slower deposition time.Thus, increasing temperature may require increased pressure. In oneembodiment, the temperature is about 5 C and the pressure about 10 Torr.

Exposure time depends on reaction conditions as well as the desired filmthickness. Deposition rates are typically from about 100 angstroms/minto 1 micrometer/min.

Showerhead (or other gas inlet) to pedestal distance should also besmall to facilitate deposition. Showerhead-pedestal distance istypically ranges from about 300 mil-5 inches. In some embodiments, itranges from about 300 mil-1 inch.

A baffle plate assembly is utilized in certain embodiments to constrictreactant flow, thereby increasing the residence time of the silicon andoxidant precursors above the wafer substrate. The baffle plate assemblyis mechanically attached to the chamber body and tends to be at the sametemperature of the chamber walls (i.e >30 C) to prevent deposition fromoccurring on the baffle plates. The change in conductance is achieved byproviding an inert gas ballast below the baffle plates. Examples ofinert gases that may be used include He, Ar and N₂. Typical flow ratesfor the ballast vary from 100 sccm to 5 slm for the inert gases. In oneembodiment a flow of 2 slm of He is used to create a ballast. Aschematic of a deposition using baffle is depicted in FIG. 6 anddiscussed further below.

Converting the Flowable Film to a Solid Oxide Film

After the flowable film is deposited on the substrate, it is convertedto a solid silicon dioxide film. According to various embodiments, thefilm may be converted to a solid oxide film by exposure to a plasma.This results in a top-down conversion of the flowable film to a solidfilm.

Oxygen, helium, argon and steam plasmas are examples of plasmas that maybe used. The plasma may also contain one or more of these compounds.Nitrogen-containing plasmas should be avoided if the incorporation ofnitrogen in the resulting dielectric film is undesirable. Temperaturesduring plasma exposure are typically about 20° C. or higher.

In certain embodiments, an oxygen or oxygen-containing plasma is used tofacilitate conversion of the Si—H bonds into Si—O bonds. Anoxygen-containing plasma may be particularly useful for flowable filmsthat have a high number of Si—H bonds, e.g., for films formed by thereaction of TEOS and steam.

Pressure is typically low, e.g., less than about 6 Torr. In certainembodiments, ultra-low pressures, on the order of about 0-10 mTorr areused during the conversion step. Using low pressure allows top-downconversion of the flowable film without leaving voids in the film.Without being bound by a particular theory, it is believed that lowpressure causes sites left vacant by the removal of —H and —OH groups tobe filled only by available oxygen radicals in the plasma. Also incertain embodiments, inductively coupled (high density) plasmas are usedto facilitate conversion.

The plasma source may be any known plasma source, including RF andmicrowave sources. In a RF plasma, plasma power is typically at leastabout 3000 W. Also the plasma-assisted conversion is preferablyperformed with a high frequency substrate bias.

In some embodiments, a thermal anneal may be used instead of or inaddition to a plasma to convert the film into a solid oxide. Thermalannealing may be performed in any suitable ambient, such as a water,oxygen or nitrogen ambient. Temperatures are typically at least about25° C., i.e. high enough to break the Si—OH bond. For example, thermallyannealing a silanol gel R—Si(OH)_(x) results in a silicon dioxide SiO₂film and water vapor.

Other Embodiments

In another embodiment, the flowable film is formed by first depositingthe silicon-containing precursor and then flowing steam to convert thefilm to the flowable liquid. An example of a process according to thisembodiment is shown in FIG. 3. As shown, the deposition process 300begins at operation 301 in which a substrate containing a gap isprovided to a reaction chamber. At operation 303, a process gascontaining a silicon-containing precursor is introduced to the reactor.In this method, the process gas introduced in operation 303 does notcontain an oxidant. Examples of silicon-containing precursors includeTES and TEOS. A diluent gas such as helium or other suitable diluent maybe used. Then in operation 305, a solid silicon-containing layer isdeposited on the substrate. Low RF power (less than about 400 W) istypically used to deposit the film. Substrate temperature is alsotypically fairly low during this step, for example, less than about 10°C. In some embodiments, the temperature may be less than about 2° C. Ina particular embodiment, the substrate temperature is subzero.

After the silicon-containing layer is deposited, a process gascontaining an oxidant is introduced to the reaction chamber in operation307. In specific example, the oxidant is H₂O (steam). The process gasmay be introduced with or without RF power. Substrate temperature istypically the same as for operation 305. The water or other oxidantoxidizes the solid film and converts it to a flowable film such as thatdescribed above with respect to operation 207 of FIG. 2 in operation309. The oxidizer in one embodiment is water with a flow rate varyingfrom 0.1 to 5 ml/min flow rate. One of skill in the art will understandthat optimal flow rates depend on the degree of oxidation achieved andfilm conversion based on the kind of silicon precursor utilized. Theflowable film is then converted to a solid silicon oxide film inoperation 311. A plasma or thermal anneal, as discussed above, may beused in operation 311.

Apparatus

The methods of the present invention may be performed on a wide-range ofreaction chambers. The methods may be implemented on any chamberequipped for deposition of dielectric film, including HDP-CVD reactors,PECVD reactors, any chamber equipped for CVD reactions, and chambersused for PDL (pulsed deposition layers).

Such a reactor may take many different forms. Generally, the apparatuswill include one or more chambers or “reactors” (sometimes includingmultiple stations) that house one or more wafers and are suitable forwafer processing. Each chamber may house one or more wafers forprocessing. The one or more chambers maintain the wafer in a definedposition or positions (with or without motion within that position, e.g.rotation, vibration, or other agitation). While in process, each waferis held in place by a pedestal, wafer chuck and/or other wafer holdingapparatus. For certain operations in which the wafer is to be heated,the apparatus may include a heater such as a heating plate.

In certain embodiments, the present invention may be implemented in aHDP CVD reactor. An example of a suitable reactor is the Speed™ reactor,available from Novellus Systems of San Jose, Calif. In certainembodiments, the present invention may be implemented in a PECVDreactor. Examples of suitable reactors are the Sequel™ reactor and theVector™ reactor, both available from Novellus Systems of San Jose,Calif. In certain embodiments, the present invention may be implementedin a CVD chamber equipped for metal and/or dielectric deposition. Anexample of a suitable reactor is the Altus™ reactor available fromNovellus Systems of San Jose, Calif. In certain embodiments, the presentinvention may be implemented in a chamber equipped for atomic layerdeposition (ALD), pulsed deposition layer (PDL), or pulsed nucleationlayer (PNL) reactions. An example of such a reactor is the Altus™ withPNL reactor available from Novellus Systems of San Jose, Calif.

In certain embodiments, the deposition and conversion operations areperformed in the same reaction chamber. In other embodiments, thedeposition may be performed in a first chamber and then transferred to asecond chamber for a thermal or plasma anneal. For example, reactorsthat are configured for plasma reactions may be used for both thedeposition and plasma anneal operations. Other reactors may be used fordeposition and thermal anneal operations.

FIG. 4 shows an example of a reactor that may be used in accordance withcertain embodiments of the invention. The reactor shown in FIG. 4 issuitable for both the dark deposition and conversion to a solid film,for example, by plasma anneal. As shown, a reactor 400 includes aprocess chamber 424, which encloses other components of the reactor andserves to contain the plasma generated by a capacitor type systemincluding a showerhead 414 working in conjunction with a grounded heaterblock 420. A low-frequency RF generator 402 and a high-frequency RFgenerator 404 are connected to showerhead 414. The power and frequencyare sufficient to generate a plasma from the process gas, for example400-700 W total energy. In the implementation of the present invention,the generators are not used during dark deposition of the flowable film.During the plasma anneal step, one or both generators may be used. Forexample, in a typical process, the high frequency RF component isgenerally between 2-60 MHz; in a preferred embodiment, the component is13.56 MHz.

Within the reactor, a wafer pedestal 418 supports a substrate 416. Thepedestal typically includes a chuck, a fork, or lift pins to hold andtransfer the substrate during and between the deposition and/or plasmatreatment reactions. The chuck may be an electrostatic chuck, amechanical chuck or various other types of chuck as are available foruse in the industry and/or research.

The process gases are introduced via inlet 412. Multiple source gaslines 410 are connected to manifold 408. The gases may be premixed ornot. The temperature of the mixing bowl/manifold lines should bemaintained at levels above the reaction temperature. Temperatures at orabove about 8° C. at pressures at or less than about 20 Torr usuallysuffice. Appropriate valving and mass flow control mechanisms areemployed to ensure that the correct gases are delivered during thedeposition and plasma treatment phases of the process. In case thechemical precursor(s) is delivered in the liquid form, liquid flowcontrol mechanisms are employed. The liquid is then vaporized and mixedwith other process gases during its transportation in a manifold heatedabove its vaporization point before reaching the deposition chamber.

Process gases exit chamber 400 via an outlet 422. A vacuum pump 426(e.g., a one or two stage mechanical dry pump and/or a turbomolecularpump) typically draws process gases out and maintains a suitably lowpressure within the reactor by a close loop controlled flow restrictiondevice, such as a throttle valve or a pendulum valve.

It should be noted that the apparatus depicted in FIG. 4 is but oneexample of an apparatus that may be used to implement this invention.

FIG. 5 provides a simple block diagram depicting various reactorcomponents arranged as may be arranged in a HDP-CVD reactor that may beused in accordance with the invention. As shown, a reactor 501 includesa process chamber 503 which encloses other components of the reactor andserves to contain the plasma. In one example, the process chamber wallsare made from aluminum, aluminum oxide, and/or other suitable material.The embodiment shown in FIG. 5 has two plasma sources: top RF coil 505and side RF coil 507. Top RF coil 505 is a medium frequency or MFRF coiland side RF coil 507 is a low frequency or LFRF coil. In the embodimentshown in FIG. 5, MFRF frequency may be from 430-470 kHz and LFRFfrequency from 340-370 kHz. However, the invention is not limited tooperation in reaction chambers with dual sources, nor RF plasma sources.Any suitable plasma source or sources may be used.

Within the reactor, a wafer pedestal 509 supports a substrate 511. Thepedestal typically includes a chuck (sometimes referred to as a clamp)to hold the substrate in place during the deposition reaction. The chuckmay be an electrostatic chuck, a mechanical chuck or various other typesof chuck as are available for use in the industry and/or research. Aheat transfer subsystem including a line 513 for supplying heat transferfluid controls the temperature of substrate 511. The wafer chuck andheat transfer fluid system can facilitate maintaining the appropriatewafer temperatures.

A high frequency RF of HFRF source 515 serves to electrically biassubstrate 511 and draw charged precursor species onto the substrate forthe deposition reaction. Electrical energy from source 515 is coupled tosubstrate 511 via an electrode or capacitive coupling, for example. Notethat the bias applied to the substrate need not be an RF bias. Otherfrequencies and DC bias may be used as well.

The process gases are introduced via one or more inlets 517. The gasesmay be premixed or not. Preferably, the process gas is introducedthrough a gas supply inlet mechanism including orifices. In someembodiments, at least some of the orifices orient the process gas alongan axis of injection intersecting an exposed surface of the substrate atan acute angle. Further, the gas or gas mixtures may be introduced froma primary gas ring 521, which may or may not direct the gases toward thesubstrate surface. Injectors may be connected to the primary gas ring521 to direct at least some of the gases or gas mixtures into thechamber and toward substrate. Note that injectors, gas rings or othermechanisms for directing process gas toward the wafer are not criticalto this invention. The sonic front caused by a process gas entering thechamber will itself cause the gas to rapidly disperse in alldirections—including toward the substrate. Process gases exit chamber503 via an outlet 522. A vacuum pump (e.g., a turbomolecular pump)typically draws process gases out and maintains a suitably low pressurewithin the reactor.

In certain embodiments, high-cost features of the Speed™ or otherHDP-CVD tool may be eliminated. For example, the present invention maybe implemented on a HDP-CVD reactor without a dome and/orturbo-molecular pumps.

As indicated above, in certain embodiments, a CVD reactor may include abaffle assembly. FIG. 6 shows an embodiment of a CVD reactor thatincludes a baffle plate assembly. As shown in FIG. 6, oxidant andsilicon-containing precursor (as well as any dopant, carrier or otherprocess gases) enter the reactor 601 through showerhead 603 abovepedestal 605, which supports the wafer. In the example depicted in FIG.6, H₂O and TES are the oxidant and silicon-containing precursor,respectively. The inert gas enters the chamber below baffle plate 607.In certain embodiments, the baffle plate is physically connected tochamber body at the gas ring. A chamber manometer may also be locatedbelow the baffles. Use of the baffle plate and inert gas ballastincreases reactant residence time.

EXPERIMENTAL

The following examples provide details illustrating aspects of thepresent invention. These examples are provided to exemplify and moreclearly illustrate these aspects of the invention and are in no wayintended to be limiting.

A flowable film was deposited in gaps on a substrate under darkconditions as described above with reference to FIG. 2. Substratetemperature was around room temperature for the deposition. Theprecursors used were TES (tri-ethoxy silane) and steam.

After deposition, the film was exposed to an oxygen plasma for 270seconds. Oxygen flow rate was 500 sccm and RF power was 9000 W. Thewafer substrate temperature during the plasma treatment was ˜500 C.

FIG. 7 shows FTIR spectra of the dark deposited flowable film and theplasma treated film. As can be seen from FIG. 6, Si—H, Si—OH and Si—Obonds are present in the dark deposited film. Treatment with an oxygenplasma results in removal of the —OH group, near elimination of the Si—Hbonds and a considerable increase in the main Si—O bond.

A similarly deposited film was exposed to helium plasma for 60 seconds.The helium plasma treatment was observed to remove the Si—OH bonds. Nochanges were observed in the Si—H bonds. A similarly deposited film wasexposed to a steam plasma for 180 seconds. The steam plasma treatmentwas observed to remove the Si—OH bonds and cause a slight decrease inSi—H bonds. A slight increase in Si—O bonds was also observed.

FIG. 8 shows a microscope image of a film deposited under conditionsthat allowed the silicon-containing precursor and oxidant reaction toreach completion. As can be seen, the image shows perfect circulargrowth spots—indicating that the reaction has reached completion.

A film was deposited with isopropyl alcohol added to steam oxidant. FIG.9 shows a microscope image of the resulting film. As can be seen in FIG.9, the microscope image shows irregular grain boundaries, unlike thecircular growth depicted in FIG. 8. Without being bound by a particulartheory, it is believed that the ethoxy group remains attached to siliconand aids in networking the film by acting as a link. This indicates thatthe addition of an alcohol inhibitor to the oxidant precursor aids inreducing the reaction rate. This reduction in reaction rate prevents thereaction from reaching completion, due to incomplete conversion of allethoxy groups caused by an oxidant deficiency.

While this invention has been described in terms of a few preferredembodiments, it should not be limited to the specifics presented above.Many variations on the above-described preferred embodiments, may beemployed. Therefore, the invention should be broadly interpreted withreference to the following claims.

What is claimed is:
 1. A method of depositing a film on a substratesurface in a reaction chamber, comprising: forming a flowable film onthe substrate surface; and exposing the flowable film to speciesgenerated from a plasma source to thereby remove Si—H bonds from theflowable film.
 2. The method of claim 1 further comprising introducingprocess gases comprising a silicon-containing compound and an oxidantinto the reaction chamber and exposing the substrate surface to theprocess gases under conditions such that the oxidant reacts with thesilicon-containing compound to form the flowable film on the substratesurface.
 3. The method of claim 2 wherein the oxidant is selected fromozone, oxygen, a peroxide and water.
 4. The method of claim 2 whereinthe substrate temperature during exposure of the substrate surface tothe process gases is between about −20° C. and 100° C.
 5. The method ofclaim 2 wherein the substrate temperature during exposure of thesubstrate surface to the process gases is between about −20° C. and 35°C.
 6. The method of claim 2 wherein the silicon-containing compound isan organo-silane or an organo-siloxane.
 7. The method of claim 2 whereinthe silicon-containing compound is selected from TMCTS, OMCTS, TEOS,TES, TMS, MTEOS, TMOS, MTMOS, DMDMOS, Diethoxy silane (DES),triphenylethoxysilane, 1-(triethoxysilyl)-2-(diethoxymethylsilyl)ethane,tri-t-butoxylsilanol and tetramethoxy silane.
 8. The method of claim 1wherein the flowable film wholly or partially fills a gap on thesubstrate.
 9. The method of claim 8 wherein the gap has an aspect ratioof at least about 10:1.
 10. The method of claim 1 forming the flowablefilm takes place under non-plasma conditions.
 11. The method of claim 1forming the flowable film takes place under plasma conditions.
 12. Themethod of claim 1, wherein the species include oxygen species.
 13. Themethod of claim 1, wherein the species include oxygen radicals.
 14. Themethod of claim 2 wherein the process gases further comprise an alcohol.15. The method of claim 14 wherein the alcohol is ethanol.
 16. Themethod of claim 15 wherein the alcohol is isopropanol.
 17. A method ofdepositing a film on a substrate surface in a reaction chamber,comprising: forming a flowable film on the substrate surface; andremoving Si—H bonds from the flowable film.
 18. The method of claim 17further comprising introducing process gases comprising asilicon-containing compound and an oxidant into the reaction chamber andexposing the substrate surface to the process gases under conditionssuch that the oxidant reacts with the silicon-containing compound toform the flowable film on the substrate surface.
 19. The method of claim17 wherein removing Si—H bonds comprises performing an oxidizing annealof the as-formed flowable film.